Integrated circuit technology has advanced to such a degree that “Dick Tracy” type phones are now possible. Furthermore, digital cellular phones are also now capable of accessing the Internet. The problem, however, is that the power supply (i.e., batteries) technology has barely advanced over the years, and is limiting the miniaturization of such communications systems. Instead, designers of personal electronics devices have had to resort to improving the technology of the devices themselves so that they conserve as much power as possible during operation.
During standby and receive mode, most communications devices use very little power. However, the power consumption does increase significantly when such a communications device needs to transmit information, such as to a cellular base station.
Wireless technology has proceeded in three distinct steps in the area of reducing the transmit power in the mobile unit to conserve battery life. A first method for reducing the transmit power accomplishes such solely with respect to functions within the control of the handheld unit itself, such as backlight timeouts. A second method has been implemented with newer digital systems where there has been provided a signaling channel from the base station to the mobile unit. This channel is used for the base station to send a feedback signal based on the current instantaneous receive level at the base station. If that receive level is high enough, the base station sends a feedback signal to the mobile unit informing it that it can reduce its transmit power. A third method is disclosed in the above cross-referenced patent application where the system monitors the trend on the power consumption during the last two or three sampling intervals, and sends a feedback signal based on the received power trend observed.
As can be seen, current methods rely on sampling signals from the battery-powered mobile units. This cannot take into consideration other factors such as the existing charge on the battery, so the range of modification of signal strength may be quite limited. Moreover, the current state of the art in wireless communications systems cannot anticipate the need to vary signal strength until the scenario has already occurred. Finally, current technology does not provide a base station with information concerning the direction of the mobile unit relative to the base station, which would be of use in a cell hand-off situation.